Second-placed Real Madrid suffered a 2-0 defeat at Real Sociedad after being reduced to 10 men early in the second half in La Liga on Tuesday, leaving Barcelona on the brink of the title.
Runaway leaders Barca, who earlier beat Osasuna 1-0, will have the chance to clinch their 27th La Liga crown with a win in their next game at city rivals Espanyol on May 14.
Barca moved to 82 points from 33 matches and extended their lead to 14 points over reigning champions Real Madrid, who have lost two of their last three league matches.
With only five games remaining, Real would only be able to reach 83 points if they win them all.
They could slip to third place on Wednesday if their city rivals Atletico Madrid win their home match against lowly Cadiz.
Real Madrid rested several key players, including Karim Benzema and Luka Modric, as they prepare for the Copa del Rey final on Saturday against Osasuna and next week's Champions League semi-final first leg at home to Manchester City.
They were also without the suspended Vinicius Jr and never looked dangerous as Sociedad took control early in game.
"The fans should not doubt us ..." defender Nacho told Movistar Plus. "In the next ten days we have the most important thing at stake... and at the beginning of the season we all would have signed up to be like this at this point."
"Logically, (we would like to be) in a different way in the league, but we have to raise our heads quickly and fight for the titles we have left."
After a slow first half, a mistake by defender Eder Militao right after the break gifted Sociedad the opener.
While putting pressure on Alexander Sorloth on the right side of the area, Militao slipped and tried to deliver a pass to goalkeeper Thibaut Courtois that was intercepted by Take Kubo who opened the scoring by tapping into an empty net.
Defender Dani Carvajal was sent off on the hour for a second yellow card after a sliding tackle on Aihen Munoz.
The hosts then extended their lead in the 84th through 21-year-old Ander Barrenetxea who ghosted behind the defence and slotted a David Silva pass between Courtois and the near post.
"We always go out to win, but in recent matches, especially away from home, we are not showing the level we should for a competition like La Liga," added Nacho.
"You can see it today: if you don't go out with intensity, anyone can beat you."
Holders Leipzig crush Freiburg
Holders RB Leipzig crushed hosts Freiburg 5-1 courtesy of a goal and three assists from Spaniard Dani Olmo on Tuesday to reach the German Cup final for the third straight year.
They will play either VfB Stuttgart or Eintracht Frankfurt, who meet on Wednesday, in the showpiece match.
In a repeat of last year's final, Leipzig, who had defender Josko Gvardiol sent off in the second half, found little resistance for most of the game from Freiburg and scored twice in 90 seconds early in the first period to take control.
Olmo's glancing header in the 13th minute put them ahead and before Freiburg had time to recover Leipzig struck again with the Spaniard feeding Benjamin Henrichs in the box to slot home.
Leipzig made it 3-0 in the 37th after another fine move and a finish from Dominik Szoboszlai, with Freiburg failing to stem the constant flow of attacks.
Nkunku made it look easy when he added another in first-half stoppage time following some more disastrous defending from the hosts and another Olmo assist.
The visitors went down to 10 men when Gvardiol was sent off after a straight red card just before the hour mark and Michael Gregoritsch's header cut the deficit in the 75th.
But it was too little too late from the hosts, whose fans interrupted the game midway through the second half when some threw objects onto the pitch and attempted to enter it.
Leipzig eased to victory as they added a fifth goal with a stoppage time penalty from Hungary international Szoboszlai.
Openda keeps Lens on track
Lens striker Lois Openda's first-half header secured a 1-0 victory over hosts Toulouse on Tuesday to tighten their grip on third place in Ligue 1 and keep them on course for a first Champions League qualification in 21 years.
Belgian Openda stooped to score his 18th Ligue 1 goal of the season after 33 minutes as he converted Massadio Haidara’s cross. Lens missed several opportunities to extend their lead in the second half, with Openda among the most wasteful.
Lens move to 69 points from 33 games, eight clear of AS Monaco for the last of the Champions League qualifying places and six behind Ligue 1 leaders Paris Saint-Germain with five rounds of matches remaining.
Lens were last in the Champions League in the 2002/03 season, having competed twice before in their history.
Toulouse looked dangerous in the first half but faded after they went behind and stay in 13th place, nine points clear of the drop zone, although they have played a game more than Brest who occupy the last of the relegation positions.